Autogenous grinding process and mill systems



Feb. 24, 1970 J. E. NELSON 3,497,142

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS 7 Original Filed Sept. 20,1963 4 Sheets-Sheet 1 lllllllllllllllllllllll PRODUCT INVENTOR. JOHN E.NELSON TTOPNL'Y.

Feb. 24, 1970 J. E. NELSON 3,

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS Original Filed Sept. 20,1963 4 Sheets-Sheet 2 mlllllllll PRODUCT INVENTOR.

JOHN E. NELSON A TOPNEX Feb. 24, 1970 J. E. NELSON AUTOGENOUS GRINDINGPROCESS AND MILL SYSTEMS Original Filed Sept. 20, 1963 4 Sheets-Sheet 5llmlmlllll llllllllllll TRODUCT INVENTOR. JOHN E. NELSON GPA/E)? Feb;24, 1970 J. E. NELSON 3,497,142

AUTOGENOUS GRINDING PROCESS AND MILL SYSTEMS Original Filed Sept. 20,1963 4 Sheets-Sheet 4 IIIIIIIIH- PRODUCT 5 INVENTOR.

JOH N r; NELSON United States Patent 3,497,142 AUTOGENOUS GRINDINGPROCESS AND MILL SYSTEMS John E. Nelson, Montreal, Quebec, Canada,assignor to Dominion Engineering Works, Limited Continuation ofapplication Ser. No. 310,271, Sept. 20, 1963. This application Oct. 10,1968, Ser. No. 781,670 The portion of the term of the patent subsequentto Oct. 17, 1935, has been disclaimed Int. Cl. 1502c 17/02, 7/00; B07b13/00 US. Cl. 241-24 4 Claims ABSTRACT OF THE DTSCLOSURE Concentrationof sizes of material in mill components of a grinding mill system forgrinding run-of-r'nine mate- 1 This is a continuation of applicationSer. No. 310,271, filed Sept. 20, 1963, now abandoned.

This invention relates to autogenous grinding mill systems or apparatusor the like and has particular reference to the provision of a new andimproved autogenous grinding mill system of the type in which coarse,friable, runof-mine material is subjected to self-reduction, and of aprocess for the removal of material of desired size from the remainderof said coarse, friable material prior to the time that such is fed intothe grinding mill.

As used herein, the term autogenous shall mean the use of a friablematerial undergoing reduction, either in whole or in part, as its owngrinding media. The term run-of-mine material, as used herein, shallmean a mixture of friable material, which mixture normally includescoarse, intermediate, and fine sizes, the larger sizes being sufficientto effect self-reduction and reduction of the smaller sizes present inthe mixture. The term ebble milling, as used herein, shall mean the useof screened fractions of the friable material in the coarse range, asmedia, for the grinding of the finer sizes of the same material.

conventionally, when a product much finer than about 10 mesh isrequired, it is, generally, not practical to produce such product in asingle mill which is being fed with run-of-mine ore. Thus,conventionally, when a finer product than about 10 mesh is required, itis usually necessary to first produce an intermediate sized product fromone grinding mill, and then to further grind this product in anadditional mill, or additional mills as the specific case may require,using the pebble milling process.

conventionally, the pebbles necessary for this pebble milling processare obtained either from the charge within the first or primary mill,through suitable ports, or from the discharge of said first mill bymeans of auxiliary apparatus.

Said conventional processes for the removal of the pebbles, however,possess certain severe inherent disadvantages and deficiencies.

In the first place, should the necessary pebbles be removed from thecharge within the first mill by means of suitable ports, material ofsizes other than that desired for use either as pebbles or as theprimary mill product 3,497,142 Patented Feb. 24, 1970 is obtained; suchmaking the provision of auxiliary apparatus necessary for the requiredseparation of the unwanted fractions of said material and either thereturning of such to the primary mill or the separate treatment of suchelsewhere. Furthermore, in the use of the port process, a furtherdisadvantage arises from the difficulty in adjusting the port size andarea to match the, generally, constantly changing requirements of thepebble mills.

Should the necessary pebbles be obtained from the discharge of thefirst, or primary, mill, a range of size of material even greater thanthat obtained through the use of the port method is obtained; saidgreater range of size of material leading to even greater problems inits higher demands for the separation and return of unwanted material.Thus, in brief, both of these conventional methods for obtaining thepebbles necessary for the pebble milling process are unsatisfactory inpractice.

An object of the invention is to provide a new and improved process andapparatus of the type set forth which includes the removal of thedesired pebbles prior to the feeding of such into the first, or primary,grinding mill.

Another object of the present invention is to provide a new and improvedprocess for the provision of pebbles for the pebble milling process,which new and improved process is simple and economical in operation.

Another object of the invention is to provide a process and apparatus ofthe type set forth which includes a provision for the supply of asufiicient quantity of suitable pebbles even should the run-of-minematerial itself, not include such suificient supply.

Another object of the invention is to provide a process and apparatus ofthe type set forth which enables pebbles of sizes other than thatdesired for said pebble milling process to be removed from therun-of-mine material prior at the same time as the pebbles necessary forsaid process are removed from said run-of-mine material.

Another object of the invention is to provide new and improved means forthe accomplishment of the foredescribed process.

Other objects and advantages of the invention will be apparent from thefollowing description taken in connection with the accompanyingdrawings. It will be understood that changes may be made in the detailsof construction and arrangement of parts shown and described as thepreferred forms of the invention have been given by way of illustrationonly.

Referring to the drawings:

FIG. 1 is a schematic view of an apparatus for the production of aground product from run-of-mine material through the use of a primaryautogenous mill and a secondary pebble mill;

FIG. 2 is a schematic view of an apparatus similar to that of FIG. 1,but which system is adapted to function when insuificient pebble sizedmaterial is present in the run of mine material;

FIG. 3 is a schematic view of an apparatus similar to those of FIGS. 1and 2, said system being adapted to remove from the run-of-minematerial, in addition to those pebbles of correct size for the pebblingprocess, those pebbles of a size larger; and

FIG. 4 is a schematic view of an apparatus similar to that of FIG. 3,but which system is adapted to remove pebbles of a size smaller than thedesired size in addition to those of the desired size.

Referring more particularly to the drawings wherein similar referencecharacters designate corresponding parts throughout the several views,and with particular reference to FIG. 1 of the drawings, suchillustrates a system for producing a ground product from run-of-minematerial through the use of a primary autogenous mill and a secondarypebble mill.

The apparatus employed as shown in FIG. 1 comprises a bin adapted tocontain run-of-mine material or ore, feeder 11 which conveys suchmaterial to the separation devices or screen 12 and 13.

The apparatus also includes primary mill 14, pebble mill 16 and volumeor quantity control means 15.

Primary mill 14 has discharge 17 which is connected to the inlet ofpebble mill 16.

In the process of the present invention and operation ot the apparatusshown in FIG. 1, run-of-mine ore from the bin 10 is transported by thefeeder 11 to the dual separation devices which comprise the screens orgrisslys 12 and 13.

Said dual separation devices are chosen for any particular applicationof the system such that said separation devices are at the upper andlower limits of the size pebbles that are required. Thus, assuming forthe purposes of example that a pebble size minus 3 inches, plus twoinches has been established, the first separation device or screen 12would be chosen such as to be operative at three inches and the secondseparation device or screen 13 would be chosen such as to be operativeat two inches.

In the embodiment of the system illustrated in FIG. 1, the plus threeinch material joins with the minus two inch material for feed to theprimary mill 14. The minus three inch-plus two inch pebbles, on theother hand, are transported through the suitable volume controllingmeans 15 to the pebble mill 16, any excess in said minus three inchplustwo inch material being fed to the primary mill 14. The primary milldischarge which is shown generally at 17 is delivered to the pebble mill16.

The mill apparatus and process, as illustrated in FIG. 1 andforedescribed, is adapted for application where the run-of-mine materialcontains a sufficient quantity of pebbles of the size required for thepebble mill; and where, also, it is neither necessary nor desired toremove certain fractions of the primary mill feed in order to maintain asuitable charge equilibrium within that mill.

With reference to FIG. 2 of the drawings, such illus trates the processof the present invention and the apparatus required where insufiicientpebble size material is present in the run-of-mine ore. In such case, asecond withdrawal point 18 from the bin 10 is provided in order that aquantity of the ore contained in said bin sufficient to produce theadditional required material of pebble size may be provided to thesystem by means of the jaw, gyratory, or other suitable crushing device20, which crushing device 20 has been set to produce pebbles of thedesired s1ze.

The discharge 21 from said crushing device feeds the ore crushed by saidcrushing device into the mainstream of the ore passing through the dualseparation devices 12 and 13.

The process and apparatus of FIG. 2 is particularly adapted forapplications where it is neither necessary nor desirable to control theprimary mill 14 charge equilibrium by the removal of sizes of materialother than that required for the operation of the pebble mill 16 beforethe admission of said material into the primary mill 14. However, if amoderate excess in capacity be produced by the crushing device 20, somedegree of control of the larger sizes of material may be obtainedthrough the operation of said crushing device at a larger setting andgreater tonage than is required for the production of the pebble sizematerial alone.

With regard to the process of the invention and apparatus illustrated inFIG. 3, such is particularly adapted for application where, in additionto the removal of pebbles of the proper size for the pebble mill, theremoval of material of a size larger than said pebble size is necessaryin order to maintain a satisfactory equilibrium within the primary mill14.

In such case, a third separation device 22 is added to separationdevices 12 and 13 and quantity control devices 23 and 24 are provided inorder that the crushing device 20 can be fed the oversize from either orboth of the separation devices 22 and 12, any excess in such joiningWith the excess of pebble size material and the underflow fromseparation device 13 for the feeding of the primary mill 14.

By way of example, assuming that minus three inchplus two inch materialis required for the pebble mill 16, and, further, that material in thesize range of minus six inch-plus three inch should be reduced, theseparation devices 22, 12, and 13 would be set at six inches, threeinches, and two inches, respectively.

With regard to FIG. 4 of the drawings, the process and apparatusillustrated therein is particularly adapted for application whereproduction of pebble size material is desired and, in addition, wherematerial a size fraction smaller than pebble size must be removed andseparately treated in order that the primary mill 14 maintain optimumcharge equilibrium.

In such case, a third separation device 25 is added to the screeningsystem, said separation device 25 being set for a size smaller thanthose pebbles required for the operation of the pebble mill 16. Theoversize material from said separation device 25 is transported by wayof a suitable quantity control device 26 to a comminuting device such asa crusher, rod, ball, or other suitable type of mill 27 for reductionbefore return to the operative portion of the system.

In this illustrated form of the system, it is assumed that one stage ofcrushing will sutfice, after which crushing, the crushed product can befed into the autogenous primary mill 14. However, in some cases, it maybe preferable to treat the oversize from the separation device 25 in arotary mill, or mills, and to deliver this product either to the primarymill feed, pebble mill feed, or finished product.

By way of specific example, assuming that minus three inch-plus two inchpebble is required for the pebble mill 16, and that pebbles less thantwo inches to more than one inch should be treated, the three screeningor separation devices 12, 13, and 25 would separate at three inches, twoinches, and one inch, respectively.

In addition to these four processes and apparatus which have beenforedescribed, it is believed to be readily apparent that manyvariations of said systems are possible. By way of example, the crushingdevice or devices, primary and secondary mill or mills can be closecircuited with the appropriate screen, classifiers, cyclones, and thelike as may be desired.

The operation of the process and apparatus herein provided is believedto be apparent from the foregoing description.

What I claim as new and desire to secure by Letters Patent 0f the UnitedStates is:

1. The method of operating a grinding mill system having an autogenousmill for grinding run-of-mine material and a pebble mill for providingfurther reduction of the material including the steps of; (1) extractingby sorting at least a portion of a predetermined range of size of pebblematerial from said run-of-mine material prior to entry of the materialinto said autogenous mill to control the size range of the input to theautogenous mill; (2) passing the residue of said run-of-mine material tothe autogenous mill together with any excess of extracted pebblematerial, for reduction by grinding; -(3) passing at least a portion ofthe output of the autogenous mill to said pebble mill for furtherreduction therein; (4) and supplying a sutficient portion of theextracted pebble material, to said pebble mill to maintain satisfactorygrinding therein, whereby operation of the system is promoted and thebuild-up of undue quantities of intermediate size material iscontrolled.

2. The method of claim 1 including the step of crushing a portion of therun-of-mine material prior to said extracting by sorting step, toprovide an increased quantity of pebble size material.

3. The method as claimed in claim 1 including the steps of extracting bysorting a portion of said run-of-mine material of a size exceeding apredetermined pebbling size, reducing said portion by crushing toprovide additional pebble material, and returning said portion for saidsorting step, whereby material larger than pebble size is removed tomaintain a desired equilibrium within said autogenous mill.

4. The method as claimed in claim 1 including the step of extracting bysorting at least a portion of material of a size less than apredetermined pebbling size, reducing said portion by comminuting apartfrom the residue, and returning the reduced material for furthermilling.

ROBERT C.

References Cited UNITED STATES PATENTS RIORDON, Primary Examiner 10 D.G. KELLY, Assistant Examiner US. Cl. X.R.

